In the production of cheroots and similar rolled tobacco articles its is common practice to make use of a combined spread- and cutting table on which a stripped tobacco leaf is held by suction after having been positioned as desired in relation to the cutting knife. A roller is subsequently moved across said knife to cut a wrapper out which by a pivot arm provided with a suction head is transferred to a roller mechanism in which the wrapper is applied to a prepared bunch. If desired, two or more wrappers can be cut out successively from each half of the tobacco leaf and the operator is then obliged, prior to the cutting operation, to position the tobacco leaf in such a manner on the table that the desired number of wrappers may be produced with due regard to possible holes or other defects in the tobacco leaf and to the location of its side ribs.
It is also known to perform the cutting in whole or half tobacco leaves independently of the overrolling. The wrappers may then be collected in bobbins for later use, but in this case too, the operator must be careful about positioning the tobacco leaves so as to reduce waste to a minimum. In this respect the operator's only aid is generally the cutting knife the location of which can be seen on the surface of the tobacco leaf after vacuum has been applied to hold the leaf, but at that time the positioning cannot be changed or corrected unless the vacuum is suspended. It is further possible, in particular by use of spread-tables without cutting knife, to mark the cutting pattern or other indications on the spread-table, but this is neither a satisfactory solution because such indications or at least considerable parts of them are hidden by the tobacco leaf as placed on the table.
The above mentioned drawback has been eliminated by a device known from DE-AS No. 1,188,995 and intended for cutting wrappers or binders one by one from tobacco leaves placed on a cutting table which is illuminated in a pattern corresponding to the contour of the wrapper or binder to be cut out. For this purpose a templet may be mounted between the top side of the table and a source of parallel light beams, the contour of said templet being identical with the cutting pattern so that the tobacco leaf is illuminated in a field contoured exactly as this pattern, or a light source may be provided below the table and surrounded by its movable knife to illuminate the field from below within the contour of the knife so that this field becomes visible through the tobacco leaf as laid.
With a view to obtaining an optimum output of tobacco leaves, and for the relief of the operator, a technique has further been developped that makes use of several cutting knives the position of which is controlled by a scanning picture of the tobacco leaf, see for instance the published specification of British patent application No. 2,015,865. In this case the tobacco leaf is placed arbitrarily on a light-translucent table and while being transilluminated from below the leaf is being scanned so as to produce a picture illustrating the positioning of the periphery and ribs of the leaf and revealing possible defects such as holes or discolorations. From said picture the positioning of the cutting knives is controlled in such a manner that only usable sections of the leaf will form part of the wrappers or binders resulting from the cutting operation. This technique requires, however, vast investments and due to the positioning or adjusting movement of the knives the rate of production will scarcely be sufficiently high to justify such investments.